Computer Chess Club Archives




Subject: Re: When to do a null move search - an experiment

Author: Vincent Diepeveen

Date: 17:45:28 04/27/04

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On April 27, 2004 at 15:06:29, Gerd Isenberg wrote:

>On April 27, 2004 at 03:33:26, Bas Hamstra wrote:
>>About double nullmove: I tested this in some pawnendgames to see if it could
>>handle zuzwang problems, but I don't see it perform any better than normal
>>nullmove. Can Vincent or you post a position where double null outperforms
>>normal null? I agree the idea is elegant, but I just don't see it work.
>Hi Bas,
>i don't use double nullmove, but a verification search with same R, if nullmove
>fails high. Some of my favorite zugzwang positions:

Seeing the zugzwang is easy here. Basically you want engines to see that the
pawn endgame after the zugzwang is not a draw but is winning for black because
it can create a passer that possibly runs faster than white ones.

All you need here is 6 men EGTB, in which case even fullwidth will solve this
easily. Of course double nullmove sees that zugzwang easily. So it is up to the
program then whether it has 6 men whether it sees soon that the pawn endgame is
a win.

A good pawnendgame evaluation would help too :)

>CTT4-11 Crafty-IsiChess:
>[D] 8/8/1p1r1k2/p1pPN1p1/P3KnP1/1P6/8/3R4 b - - ; bm Nxd5
>[D] 4KBkr/7p/6PP/4P3/8/3P1p2/8/8 w - - ; bm g7


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